Studies will be continued on the effect of coccidiosis on the pH of the intestine. It has been found that Eimeria acervulina which parasitizes the upper intestine causes a drop in the pH which is not related to the presence of bacteria. Additional studies are in progress with E. brunetti to determine if a species infecting the lower intestine will also produce a decrease in pH in the absence of bacteria. Future studies will also investigate the decrease in serum xanthrophyll level in chickens infected with all species of coccidia. Investigations will be directed toward understanding the relationship between coccidia and bacteria with emphasis on elucidating the role they play in the interaction between pH and xanthrophyll levels. Efforts will also be directed towards a study of obligate anaerobic bacteria and their relationship with E. tenella, the parasite causing cecal coccidiosis. These organisms are difficult to culture, though they comprise over 97% of the fecal flora. Experiments to isolate, characterize and identify the most predominant organisms of the cecum will be conducted. A single isolate can then be introduced in gnotobiotic studies with monoisolates.